Apparatus for driving motor and controlling method thereof

ABSTRACT

Disclosed herein is an apparatus for driving a motor, the apparatus including: an inverter applying a direct current voltage to each phase of a brushless direct current (BLDC) motor by a switching operation; a reference voltage generating unit generating at least one reference voltage using a voltage of a neutral point of the BLDC motor; and a motor driver detecting a zero cross point (ZCP) of back electromotive force of each phase by comparing a phase voltage of each phase of the BLDC motor with the reference voltage and generating a PWM signal for controlling the switching operation of the inverter and a phase switching of each phase using information of a position of the zero cross point (ZCP).

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2013-0123540, filed on Oct. 16, 2013, entitled “Apparatus for DrivingMotor and Controlling Method thereof”, which is hereby incorporated byreference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an apparatus for driving a motor and acontrolling method thereof.

2. Description of the Related Art

In general, since a direct current motor (DC motor) has a linearrelationship between an applied voltage and a speed, it has a simplespeed control and a wide speed control range. However, the DC motor hasa brush as an essential component to maintain torque in one direction.Therefore, it was difficult to drive at a high speed due to the brush,maintenance was frequent due to abrasion of the brush, and a noise, orthe like was serious.

In order to solve the above-mentioned problems, a brushless DC motor(called a BLDC motor) was suggested, wherein the brushless DC motor isconfigured by a stator having a coil wound in a direction opposite to atypical DC motor and a rotor having a permanent magnet and obtainsrotation force by controlling a current flowing in the coil of thestator to thereby control magnetic flux of the stator and magnetic fluxof the permanent magnet of the rotor so as to have a right angle or anyangle.

Since the BLDC motor does not include the brush, it solves disadvantagesof the DC motor according to the prior art, and since it has advantagesof the DC motor as it is, it has been recently and widely used. In orderto appropriately control magnetic flux, a switching state of an inverterswitching devices need to be determined so that a magnetic generationposition of the stator is determined depending on a position of therotor. In order to detect the position of the rotor, even though asensor such as a hall sensor, or the like may be used, a sensor-lessscheme detecting position information of the rotor by detecting a zerocross point (ZCP) by back electromotive force without using the sensoris mainly used due to environmental factors such as a temperature, apressure, and the like.

Therefore, in the above-mentioned sensor-less scheme, according to theprior art, as described in the following prior art document, the zerocross point (ZCP) is detected by comparing the back electromotive forceof each phase induced from the stator with a reference voltage. In theBLDC motor, in the case in which an error is generated in the phasevoltage and the reference voltage due to mismatch of an inductor, andthe like, an accuracy of the detection of the zero cross point (ZCP) isdecreased, such that a position detection of the rotor may become unevenand a timing of switching a phase of the motor may become irregular.

PRIOR ART DOCUMENT Patent Document

-   (Patent Document 1) 2006-0068844KR

SUMMARY OF THE INVENTION

The present invention has been made in an effort to provide an apparatusfor driving a motor capable of more accurately detecting a zero crosspoint (ZCP) by comparing back electromotive force of each phase with atleast one reference voltage in order to secure reliability in driving aBLDC motor, and a controlling method thereof.

According to a preferred embodiment of the present invention, there isprovided an apparatus for driving a motor, the apparatus including: aninverter applying a direct current voltage to each phase of a brushlessdirect current (BLDC) motor by a switching operation; a referencevoltage generating unit generating at least one reference voltage usinga voltage of a neutral point of the BLDC motor; and a motor driverdetecting a zero cross point (ZCP) of back electromotive force of eachphase by comparing a phase voltage of each phase of the BLDC motor withthe reference voltage and generating a PWM signal for controlling theswitching operation of the inverter and a phase switching of each phaseusing information of a position of the zero cross point (ZCP).

The inverter may include transistors controlled by the PWM signal of themotor driver and diodes each connected to the transistors inanti-parallel.

The reference voltage generating unit may generate first and thirdreference voltage having a predetermined voltage difference with asecond reference voltage based on a voltage of a neutral point as thesecond reference voltage.

The motor driver may include a plurality of comparators for each phaseand a plurality of registers connected to the comparators in series, theback electromotive force may be input to each of the non-invertingterminals of the comparators, the plurality of reference voltage may beinput to each of the inverting terminals, and outputs of the comparatorsmay be stored in the registers.

The motor driver may include: a ZCP detecting module detecting the zerocross point (ZCP) of each phase by each comparing the back electromotiveforce of each phase with at least one reference voltage; a controllingmodule measuring a position and a rotation speed of a rotor usinginformation of the detected zero cross position; and a PWM signalgenerating module generating a PWM signal for controlling a phaseswitching timing of each phase based on the position of the rotor andspeed information of the motor.

The motor driver may include an initial driving circuit providinginformation for the zero cross point (ZCP) for the phase switching ofeach phase to the PWM signal generating module at the time of an initialdrive.

The ZCP detecting module may include a U phase detecting circuit, a Vphase detecting circuit, and a W phase detecting circuit each includinga plurality of comparators and a plurality of registers connected to thecomparators in series, the back electromotive force of each phase may beinput to non-inverting terminals of the comparators of the detectingcircuit of each phase, the plurality of reference voltage may be inputto each of the inverting terminals, and outputs of the comparators maybe sequentially stored in the registers.

The register may be a flip-flop.

The controlling module may include: a position measuring circuitmeasuring the position of the rotor using information of a position atwhich the zero cross point is generated; a speed measuring circuitmeasuring the speed of the rotor using information of a time interval atwhich the zero cross point is generated; and a controller controlling aphase switching of each phase by the PWM signal generating module basedon the position of the rotor and speed information of the motor.

The PWM signal generating module may include: a PWM generating circuitgenerating a PWM signal applied with a duty ratio determined by thecontroller in order to control the rotation speed of the rotor; adriving signal generating circuit generating a driving voltage forderiving the phase switching of each phase using the PWM signal; and agate driver operating transistors of the inverter using the drivingsignal based on phase switching information of each phase applied fromthe controller.

According to another preferred embodiment of the present invention,there is provided a controlling method of an apparatus for driving amotor, the controlling method including: generating at least onereference voltage; detecting a zero cross point (ZCP) determiningwhether or not the zero cross point (ZCP) is detected by comparing aphase voltage of each phase of a BLDC motor with the reference voltage;and determining a phase switching determining whether or not the phaseswitching of each phase is performed depending on whether or not thezero cross point (ZCP) is detected.

In the generating of the reference voltage, first and third referencevoltage having a predetermined voltage difference with a secondreference voltage may be generated based on a voltage of a neutral pointas the second reference voltage.

The detecting of the zero cross point may include: comparing backelectromotive force of each phase input to each of the non-invertingterminals of a plurality of comparators provided for each phase with atleast one reference voltage; storing each of the outputs of theplurality of comparators of each phase by a plurality of registers; anddetermining whether or not the zero cross point is detected based ondata stored in the register.

In the case in which the zero cross point (ZCP) is detected, thedetermining of the phase switching may include: measuring a position anda rotation speed of a rotor using information of the detected zero crosspoint (ZCP); generating a PWM signal based on the position and therotation speed of the rotor; and controlling the performing of the phaseswitching of each phase by a switching operation of an inverter usingthe PWM signal.

In the case in which the zero cross point (ZCP) is not detected, in thedetermining of the phase switching, the comparing of the phase voltageof each phase of the BLDC motor with the reference voltage may bere-performed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more clearly understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a block diagram showing an apparatus for driving a motoraccording to a preferred embodiment of the present invention;

FIG. 2 is an entire circuit diagram showing the apparatus for drivingthe motor according to the preferred embodiment of the presentinvention;

FIG. 3A is a circuit diagram showing a ZCP detecting module according tothe preferred embodiment of the present invention and FIG. 3B is acircuit showing a U phase detecting circuit included in the ZCPdetecting module;

FIGS. 3C and 3D are views showing output patterns of first to thirdcomparators included in the U phase detecting circuit;

FIGS. 4A and 4B are views showing phase voltage of a BLDC motor and atiming of performing the phase voltage of each phase according to apreferred embodiment of the present invention; and

FIG. 5 is a view showing a controlling method of the apparatus fordriving the motor according to a preferred embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The objects, features and advantages of the present invention will bemore clearly understood from the following detailed description of thepreferred embodiments taken in conjunction with the accompanyingdrawings. Throughout the accompanying drawings, the same referencenumerals are used to designate the same or similar components, andredundant descriptions thereof are omitted. Further, in the followingdescription, the terms “first”, “second”, “one side”, “the other side”and the like are used to differentiate a certain component from othercomponents, but the configuration of such components should not beconstrued to be limited by the terms. Further, in the description of thepresent invention, when it is determined that the detailed descriptionof the related art would obscure the gist of the present invention, thedescription thereof will be omitted.

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

Hereinafter, an apparatus for driving a motor and a controlling methodthereof according to a preferred embodiment of the present inventionwill be described in detail with reference to the accompanying drawings.A zero cross point (ZCP) refers to a point at which back electromotiveforce (phase voltage) of each phase crosses a reference voltage.

FIG. 1 is a block diagram showing an apparatus for driving a motoraccording to a preferred embodiment of the present invention, FIG. 2 isan entire circuit diagram showing the apparatus for driving the motoraccording to the preferred embodiment of the present invention, and FIG.5 is a flowchart showing a controlling method of the apparatus fordriving the motor according to a preferred embodiment of the presentinvention.

As shown in FIG. 1, an apparatus 10 for driving a motor according to apreferred embodiment of the present invention is configured to includeinput power 600, a rectifying unit 500, a motor driver 100, an inverter300, a reference voltage generating unit 200, and a BLDC motor 400.

The rectifying unit 500 includes a rectifier 510 receiving andrectifying the input power (alternating current) 600 and a smoothingcapacitor 520 smoothing the rectified input power 600, and applies therectified and smoothed direct current (DC) voltage to the inverter 300.

The inverter 300 may be applied with the rectified and smoothed directcurrent voltage by the rectifying unit 500, may apply the direct currentvoltage to each phase of the BLDC motor through a switching operation,may include transistors controlled by a PWM signal of the motor driver100 and diodes each connected to the transistors in anti-parallel, andmay be applied with the direct current voltage by a direct current (DC)instead of the rectifying unit 500.

The reference voltage generating unit 200 generates at least onereference voltage using a voltage of a neutral point N of the BLDC motor(S100). That is, the reference voltage generating unit 200 generatesfirst and third reference voltage having a predetermined voltagedifference with a second reference voltage based on the voltage of theneutral point N as the second reference voltage to thereby apply thefirst and third reference voltage to the motor driver 100.

The motor driver 100 compares a phase voltage of each phase (U phase, Vphase, or W phase) of the BLDC motor and the reference voltage (thefirst to third reference voltage) to thereby detect a zero cross point(ZCP) of back electromotive force (phase voltage) of each phase, andgenerates the PWM signal for controlling the switching operation of theinverter 300 and a phase switching of each phase using positioninformation of the zero cross point (ZCP) in the case in which the zerocross point (ZCP) is detected.

In addition, the motor driver 100 includes a plurality of comparators(first to third comparators) for each phase (U phase, V phase, or Wphase) and a plurality of registers connected to the comparators inseries, in a floating section, the back electromotive force (phasevoltage) of each phase (U phase, V phase, or W phase) is input to eachof the non-inverting terminals (+) of the comparators, the plurality ofreference voltage are input to each of the inverting terminals (−), andoutputs of the comparators are sequentially stored in the registers.

In addition, the motor driver 100 may include an initial driving circuit130 providing information for the zero cross point (ZCP) for the phaseswitching of each phase to the PWM signal generating circuit 140 at thetime of an initial drive, and may include a ZCP detecting module 110, acontrolling module 120, and the PWM signal generating module 140.

Here, the ZCP detecting module 110 each compares the back electromotiveforce (phase voltage) of each phase and at least one reference voltageby the plurality of comparators and registers for each phase (S110) tothereby detect the zero cross point (ZCP) of each phase (S120). Adescription thereof will be made below.

The controlling module 120 may measure a position and a rotation speedof a rotor using information of the detected zero cross point (ZCP), andthe like, and may include a position measuring circuit 121, a speedmeasuring circuit 122, and a controller 123.

Here, the position measuring circuit 121 measures the position of therotor using information of the position (see FIG. 4) at which the zerocross point (ZCP) is generated during a driving process of the BLDCmotor (S130), the speed measuring circuit 122 measures the speed of therotor using information of a time interval at which the zero cross point(ZCP) is generated (S140), and the controller 123 generates the PWMsignal by the PWM signal generating module based on the position of therotor and speed information of the motor to thereby control the phaseswitching of each phase (U phase, V phase, or W phase).

The PWM signal generating module 140 generates the PWM signal forcontrolling a phase switching timing of each phase based on the positionof the rotor and speed information of the motor, and may include a PWMgenerating circuit 141, a driving signal generating circuit 142, and agate driver 143.

Here, i) the PWM generating circuit 141 generates the PWM signal appliedwith a duty ratio determined by the controller in order to control therotation speed of the rotor (S150), ii) the driving signal generatingcircuit 142 generates a driving voltage for deriving the phase switchingof each phase using the PWM signal, iii) the gate driver 143 controls aswitching operation (switch on/off) of the transistor of the inverter300 by amplifying the driving signal based on phase switchinginformation (the zero cross point, the detection position, and the like)of each phase applied from the controller 123 (S160), and the phaseswitching of each phase is performed by the switching operation of theinverter 300 (S170).

Hereinafter, a process of detecting the zero cross point (ZCP) in eachphase in the ZCP detecting module will be described in detail withreference to FIGS. 3A to 3D.

FIG. 3A is a circuit diagram showing a ZCP detecting module according tothe preferred embodiment of the present invention, FIG. 3B is a circuitdiagram showing a U phase detecting circuit included in the ZCPdetecting module, and FIGS. 3C and 3D are views showing output patternsof first to third comparators included in the U phase detecting circuit.

As shown in FIG. 3A, the ZCP detecting module 110 includes a U phasedetecting circuit 111, a V phase detecting circuit 112, and a W phasedetecting circuit 113 detecting the zero cross point (ZCP) of each phaseby comparing the back electromotive force of each phase with a pluralityof reference voltage, where the detecting circuits 111, 112, and 113 ofeach phase includes a plurality of comparators 114, 115, and 116 and aplurality of registers 117, 118, and 119 each connected to therespective comparators in series. Here, the registers 117, 118, and 119may be a flip-flop.

That is, as shown in FIG. 3B, the U phase detecting circuit 111 mayinclude three comparators 114, 115, and 116, where non-invertingterminals (+) of the respective comparators are commonly input with theback electromotive force (phase voltage) of the U phase, and invertingterminals (−) thereof are input with first to third reference voltage,respectively.

In addition, the first register 117 includes a plurality of registers(Reg_(—)1 to Reg_N) connected to the first to third comparators 114,115, and 116, respectively, and outputs of the first to thirdcomparators 114, 115, and 116 are sequentially stored in the pluralityof registers (Reg_(—)1 to Reg_N), respectively.

For example, as shown in FIG. 3C, the non-inverting terminals (+) of therespective comparators included in the U phase detecting circuit 111 arecommonly input with the back electromotive force (phase voltage) of theU phase, and the inverting terminals (−) thereof are input with thefirst to third reference voltage, respectively. In addition, thecomparators 114, 115, and 116 output a high (H) or low (L) signal by acomparison between the back electromotive force (phase voltage) of the Uphase and the first to third reference voltage, the plurality ofregisters (Reg_(—)1˜Reg_N) included in the first register 117 store anoutput data pattern (FIG. 3C) in which the high (H) or low (L) signal issequentially stored, and the plurality of registers (Reg_(—)1˜Reg_N)connected to the respective comparators 114, 115, and 116 store theoutput data pattern as mentioned above.

That is, as shown in FIG. 3C, in the case in which an error (due to amismatch of an inductor, or the like) is not generated between the backelectromotive force (phase voltage) of the U phase and the secondreference voltage (a voltage of the neutral point N=V_(DD)/2), the zerocross point (ZCP) of the U phase is detected at three points Z₁, Z₂, andZ₃ by the first to third comparators, and a real zero cross point may bea cross point Z₂ of the second reference voltage (a voltage of theneutral point N=V_(DD)/2) and the back electromotive force (phasevoltage) of the U phase.

However, as shown in FIG. 3D, in the case in which the error (due to amismatch of an inductor of the motor, or the like) is generated betweenthe back electromotive force (phase voltage) of the U phase and thesecond reference voltage (a voltage of the neutral point N=V_(DD)/2),even though the zero cross point (ZCP) between the back electromotiveforce (phase voltage) of the U phase and the second reference voltage (avoltage of the neutral point N=V_(DD)/2) may not be generated, the zerocross point (ZCP) may be detected by comparing the first to thirdreference voltage with the back electromotive force (phase voltage) ofthe U phase by the plurality of comparators 114, 115, and 116.

That is, due to the error generated between the back electromotive force(phase voltage) of the U phase and the first to third reference voltage,the third reference voltage becomes lower than the back electromotiveforce (phase voltage) of the U phase, such that the zero cross point(ZCP) of the U phase may be detected at two points Z₄ and Z₅ by thefirst and second comparators 114 and 115, but the zero cross point (ZCP)between the back electromotive force (phase voltage) of the U phase andthe third reference voltage in the third compartor 116 may not begenerated.

Therefore, the real zero cross point of the U phase is a cross point ofthe second reference voltage (a voltage of the neutral point N=V_(DD)/2)and the back electromotive force (phase voltage) of the U phase.However, considering that magnitude of the first to third referencevoltage becomes low by a predetermined portion due to the errorgenerated between the back electromotive force (phase voltage) and thefirst to third reference voltage, the real zero cross point of the Uphase may be a cross point Z₄ of the first reference voltage higher thanthe second reference voltage (a voltage of the neutral point N=V_(DD)/2)by a predetermined voltage and the back electromotive force (phasevoltage) of the U phase.

As described above, in the sensor-less scheme detecting positioninformation of the rotor by detecting the zero cross point by the backelectromotive force of each phase, the apparatus for driving the motoraccording to the preferred embodiment of the present invention maysecure accuracy of the detection of the zero cross point (ZCP) and thephase switching timing of each phase and may implement an optimal BLDCmotor control by analyzing the pattern of output data stored in theplurality of register to thereby detect the zero cross point (ZCP) ofeach phase, even in the case in which the error is generated between theback electromotive force and the reference voltage due to the mismatchof the inductor of the motor, or the like.

Hereinafter, a process of performing the phase switching of each phaseaccording to the back electromotive force (phase voltage) of each phaseand the position of the zero cross point (ZCP) in the apparatus fordriving the motor according to the preferred embodiment of the presentinvention will be described in detail with reference to FIGS. 4A and 4B.

FIG. 4A is a view showing a phase voltage form of each phase of the BLDCmotor and FIG. 4B is a view showing a circuit diagram for performing thephase switching of each phase according to the detection position of thezero cross point (ZCP) of each phase.

As shown in FIG. 4A, the phase voltage of each phase of the BLDC motoris changed in a trapezoidal shape, and each phase (U phase, V phase, orW phase) includes a section to which power (V_(dd)) is applied, a groundsection (GND), and a floating section (a section to which power is notapplied) H (a dotted line region). In addition, through a to f steps,the rotor (not shown) of the motor is rotated 360°, and in general, whenthe zero cross point (ZCP) is detected, the phase switching is performedafter an electrical angle of 30° therefrom.

That is, referring to FIGS. 4A and 4B, i) in a section a, first andsixth transistors (hereinafter, referred to as TR) are switched on bythe motor driver, such that the U phase may become a power V_(dd) state,the V phase may become a GND state, and the W phase may become afloating state, and the zero cross point (ZCP) may be detected at the Wphase, ii) in a section b, the first and second TRs are switched on bythe motor driver, such that the U phase may become the power V_(dd)state, the V phase may become the floating state, and the W phase maybecome the GND state, and the zero cross point (ZCP) may be detected atthe V phase, and iii) in a section c, the third and second TRs areswitched on by the motor driver, such that the U phase may become thefloating state, the V phase may become the power V_(dd) state, and the Wphase may become the GND state, and the zero cross point (ZCP) may bedetected at the U phase.

In addition, iv) in a section d, the fourth and third TRs are switchedon by the motor driver, such that the U phase may become the GND state,the V phase may become the power V_(dd) state, and the W phase maybecome the floating state, and the zero cross point (ZCP) may bedetected at the W phase, v) in a section e, the fourth and fifth TRs areswitched on by the motor driver, such that the U phase may become theGND state, the V phase may become the floating state, and the W phasemay to become the power V_(dd) state, and the zero cross point (ZCP) maybe detected at the V phase, and vi) in a section f, the sixth and fifthTRs are switched on by the motor driver, such that the U phase maybecome the floating state, the V phase may become the GND state, and theW phase may become the power V_(dd) state, and the zero cross point(ZCP) may be detected at the U phase.

As described above, the apparatus for driving the motor according to thepreferred embodiment of the present invention may more accurately detectthe zero cross point (ZCP) of each phase and secure reliability for thetiming of performing the phase switching of each phase by generating theplurality of reference voltage having a predetermined voltage differencebased on the neutral point N by the ZCP detecting module and thereference voltage generating unit and comparing the reference voltagewith the back electromotive force of each phase by the plurality ofcomparators.

According to the preferred embodiment of the present invention, the zerocross point (ZCP) of each phase may be more accurately detected bygenerating the plurality of reference voltage having a predeterminedvoltage difference based on the neutral point N by the ZCP detectingmodule and the reference voltage generating unit of the apparatus fordriving the BLDC motor and comparing the reference voltage with the backelectromotive force of each phase by the plurality of comparators.

In addition, in the sensor-less scheme detecting position information ofthe rotor by detecting the zero cross point by the back electromotiveforce of each phase, even in the case in which the error is generatedbetween the back electromotive force and the reference voltage due tothe mismatch of the inductor of the motor, or the like, the accuracy ofthe detection of the zero cross point (ZCP) and the phase switchingtiming of each phase may be secured and the optimal BLDC motor controlmay be implemented by analyzing the pattern of output data stored in theplurality of register included the ZCP detecting circuit of each phaseto thereby detect the zero cross point (ZCP) of each phase.

Although the embodiments of the present invention have been disclosedfor illustrative purposes, it will be appreciated that the presentinvention is not limited thereto, and those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the invention.

Accordingly, any and all modifications, variations or equivalentarrangements should be considered to be within the scope of theinvention, and the detailed scope of the invention will be disclosed bythe accompanying claims.

What is claimed is:
 1. An apparatus for driving a motor, the apparatuscomprising: an inverter applying a direct current voltage to each phaseof a brushless direct current (BLDC) motor by a switching operation; areference voltage generating unit generating at least one referencevoltage using a voltage of a neutral point of the BLDC motor; and amotor driver detecting a zero cross point (ZCP) of back electromotiveforce of each phase by comparing a phase voltage of each phase of theBLDC motor with the reference voltage and generating a PWM signal forcontrolling the switching operation of the inverter and a phaseswitching of each phase using information of a position of the zerocross point (ZCP).
 2. The apparatus as set forth in claim 1, wherein theinverter includes transistors controlled by the PWM signal of the motordriver and diodes each connected to the transistors in anti-parallel. 3.The apparatus as set forth in claim 1, wherein the reference voltagegenerating unit generates first and third reference voltage having apredetermined voltage difference with a second reference voltage basedon a voltage of a neutral point as the second reference voltage.
 4. Theapparatus as set forth in claim 1, wherein the motor driver includes aplurality of comparators for each phase and a plurality of registersconnected to the comparators in series, the back electromotive force ofeach phase is input to each of the non-inverting terminals of thecomparators, the plurality of reference voltage are input to each of theinverting terminals, and outputs of the comparators are sequentiallystored in the registers.
 5. The apparatus as set forth in claim 1,wherein the motor driver includes: a ZCP detecting module detecting thezero cross point (ZCP) of each phase by each comparing the backelectromotive force of each phase with at least one reference voltage; acontrolling module measuring a position and a rotation speed of a rotorusing information of the detected zero cross position; and a PWM signalgenerating module generating a PWM signal for controlling a phaseswitching timing of each phase based on the position of the rotor andspeed information of the motor.
 6. The apparatus as set forth in claim5, wherein the motor driver includes an initial driving circuitproviding information for the zero cross point (ZCP) for the phaseswitching of each phase to the PWM signal generating module at the timeof an initial drive.
 7. The apparatus as set forth in claim 5, whereinthe ZCP detecting module includes a U phase detecting circuit, a V phasedetecting circuit, and a W phase detecting circuit each including aplurality of comparators and a plurality of registers connected to thecomparators in series, the back electromotive force of each phase isinput to non-inverting terminals of the comparators of the detectingcircuit of each phase, the plurality of reference voltage are input toeach of the inverting terminals, and outputs of the comparators aresequentially stored in the registers.
 8. The apparatus as set forth inclaim 7, wherein the register is a flip-flop.
 9. The apparatus as setforth in claim 5, wherein the controlling module includes: a positionmeasuring circuit measuring the position of the rotor using informationof a position at which the zero cross point is generated; a speedmeasuring circuit measuring the speed of the rotor using information ofa time interval at which the zero cross point is generated; and acontroller controlling a phase switching of each phase by the PWM signalgenerating module based on the position of the rotor and speedinformation of the motor.
 10. The apparatus as set forth in claim 9,wherein the PWM signal generating module includes: a PWM generatingcircuit generating a PWM signal applied with a duty ratio determined bythe controller in order to control the rotation speed of the rotor; adriving signal generating circuit generating a driving voltage forderiving the phase switching of each phase using the PWM signal; and agate driver operating transistors of the inverter using the drivingsignal based on phase switching information of each phase applied fromthe controller.
 11. A controlling method of an apparatus for driving amotor, the controlling method comprising: generating at least onereference voltage; detecting a zero cross point (ZCP) determiningwhether or not the zero cross point (ZCP) is detected by comparing aphase voltage of each phase of a BLDC motor with the reference voltage;and determining a phase switching determining whether or not the phaseswitching of each phase is performed depending on whether or not thezero cross point (ZCP) is detected.
 12. The controlling method as setforth in claim 11, wherein in the generating of the reference voltage,first and third reference voltage having a predetermined voltagedifference with a second reference voltage are generated based on avoltage of a neutral point as the second reference voltage.
 13. Thecontrolling method as set forth in claim 11, wherein the detecting ofthe zero cross point includes: comparing back electromotive force ofeach phase input to each of the non-inverting terminals of a pluralityof comparators provided for each phase with at least one referencevoltage; storing each of the outputs of the plurality of comparators ofeach phase by a plurality of registers; and determining whether or notthe zero cross point is detected based on an output data pattern storedin the register.
 14. The controlling method as set forth in claim 11,wherein in the case in which the zero cross point (ZCP) is detected, thedetermining of the phase switching includes: measuring a position and arotation speed of a rotor using information of the detected zero crosspoint (ZCP); generating a PWM signal based on the position and therotation speed of the rotor; and controlling the performing of the phaseswitching of each phase by a switching operation of an inverter usingthe PWM signal.
 15. The controlling method as set forth in claim 11,wherein in the case in which the zero cross point (ZCP) is not detected,in the determining of the phase switching, the comparing of the phasevoltage of each phase of the BLDC motor with the reference voltage isre-performed.